What is Distance?

Distance is a Windows-based computer package that allows you to design and analyze distance sampling surveys of wildlife populations. The latest version of Distance is 6.0.  Distance has been downloaded by over 18,000 users from around 135 countries.

The concepts and analysis methods used by Distance are described in the following books:

The first book describes the standard methods in detail, as well as covering aspects of survey design and giving several worked examples.  It is an essential companion to the software.  The second book covers more advanced methods, and is an essential pre-requisite to trying these methods out using the software.

A screen-shot of Distance 6.0, showing some output from the multiple covariate distance sampling analysis engine.

A screen-shot of Distance 6.0, showing some output from the mark recapture distance sampling analysis engine.

A screen-shot of Distance 6.0, showing some output from the density surface modelling analysis engine.

A screen-shot of Distance 6.0, showing some output from the survey design engine.

History of Distance

Distance evolved from program TRANSECT. However, Distance is quite different from its predecessor as a result of changes in analysis methods and expanded capabilities. The name Distance was chosen because it can be used to analyze several forms of distance sampling data: line transect, point transect (variable circular plot) and cue-counts. By contrast TRANSECT was designed only to analyze line transect data.

Distance versions 1.0 - 2.2 were DOS-based applications that were programmed using a relatively simple command language. Version 3.0 was a windows console application, but retained the command language structure. All of these versions were principally programmed by Jeff Laake of the National Marine Mammal Laboratory, US Fisheries Service.

In 1997, Steve Buckland and David Borchers, from the University of St Andrews, obtained funding from two British research councils to proceed with an ambitious three-year project to develop new distance sampling software. The new software, which became known as Distance 4, was designed to be fully windows-based, and be capable of incorporating new features such as geographic survey design, multiple covariate distance sampling models, spatial estimation of abundance, and dual observer mark-recapture line transect methods. A Distance 4 project development team was assembled, coordinated by Len Thomas. In autumn 1997, it was decided to produce an intermediate version of Distance: fully windows based, but with the same analysis capabilities as the current version 3.0. This new program, Distance 3.5, took one full year to develop, and was released in November 1998, with various updates through to February 1999. Distance 3.5 was downloaded by over 4000 users, from around 120 countries. 

Extension of Distance 3.5 to become Distance 4 began in 1999, and the software was first previewed at training workshops in summer 2000. After various public beta versions, Distance 4.0 was released in 2002, followed by Distance 4.1 in 2003 and Distance 5.0 in 2006. This last version has a major new feature in the form of a link to the free statistical software R, thereby facilitating a major expansion in the analytical capabilities potentially available to Distance users. Distance 6.0 makes use of this feature, since it contains a density surface modeling analysis engine, written as a library in R. Distance 6 was released in July 2009.

We are still actively developing the software, incorporating new features and extending current ones. If you have any comments or suggestions about the program, we’d love to hear from you!